Many viral transcripts contain structured RNA elements that regulate critical viral functions through RNA/protein interactions. The goal of this research is the discovery of novel small non-oligonucleotide compounds that inhibit the replication of the human hepatitis B virus (HBV) by binding to specific RNA structures of the HBV pregenome. In phase I of this program, a novel high throughput assay to Screen for Compounds with Affinity for Nucleic acid targets (SCAN) was developed. In Phase II, SCAN will be used to screen compound libraries and natural product collections for compounds that specifically bind to a structured RNA element of HBV. Compounds identified in the screen will be tested for specificity in secondary assays including heterologous-target SCAN assays, translation, and other assays. Compounds with specific affinity for the target RNA will be tested for toxicity in tissue culture and non-toxic compounds will be assayed for inhibition of HBV replication in 2.215 cells. Compounds with antiviral activity will be improved by structure activity relationship (SAR) studies and combinatorial chemistry. In phase III the lead compounds will be tested in animal models (woodchucks) and further improved by medicinal chemistry. PROPOSED COMMERCIAL APPLICATION: The ultimate objetive of this program is to develop effective therapeutic drugs for treatment of HBV infections. Nearly 300,3000 Americans are infected with HBV each year, however no effective antiviral therapy is available to treat these cases. Development of a new class of antiviral drugs that inhibit replication of HBV represents a major contribution to medicine and an excellent commercial opportunity.